Preparation Of Acetylcholinesterase Biosensor For Pesticide Residues Based On Nanometer M Aterials

In this paper,the preparation of nanomaterial-based biosensors for pesticide residues was proposed.The main detection object is organophosphorus pesticides(OPs).For this purpose,a series of biosensors based on acetylcholinesterase(AChE)have been constructed and were used to detect OPs with satisfactory results.The methods have high sensitivity,relatively simple experimental operation,and fast detection speed,and are also used in the detection of real samples.The main contents of this paper are as follows:Chapter 1:The some relevant introduction of OPs was described,as well as some related hazards to the human body and the environment.It also introduces the role of nanoparticles and AChE used in the experiment,and briefly describes the research work of the entire paper.Chapter 2:A kind of sensitive,rapid,and simple spectrophotometry based on a Ytterbium(Yb3+)functionalized gold nanoparticle(AuNPs-Yb)was developed for detection of OPs.Prepared AuNPs possess oxygen-containing functional groups and strong complexation reaction with Yb3+.While oxygen-containing thiophosphate in the OPs molecule can combine with Yb3+ as a cross-linking molecule to produce insoluble yetterbium phosphate,resulting in the aggregation of AuNPs and great decrease in ultraviolet absorbance strength at 520 nm by ultraviolet visible(UV-vis)spectrophotometer.Under the optimized conditions,a linear relationship between the absorbance of AuNPs and OPs concentration ranged from 0.05 mg/L to 6.0 mg/L with limit of detection for 0.03 mg/L(S/N=3),which is far lower than the maximum residue limit(0.01 ppm)in the European Union pesticides database.Therefore,this assay has potential application in the determination of OPs in the field of environmental and food monitoring.Chapter 3:A highly sensitive and selective method was developed for both UV-vis spectrophotometric and fluorimetric determination of OPs.This method uses silver nanoparticles(AgNPs)modified with graphitic carbon nitride(g-C3N4).The AgNPs reduce the fluorescence intensity of g-C3N4.Acetylthiocholine(ATCh)can be catalytically hydrolyzed by acetylcholinesterase to form thiocholine,which induces aggregation of the AgNPs.This aggregation leads to the recovery of the blue fluorescence of g-C3N4,with excitation/emission peaks at 310/460 nm.This fluorescence intensity can be reduced again in the presence of OPs because of the inhibitory effect of OPs on the activity of AChE.The degree of reduction was found to be proportional to the concentration of the OPs,and the limit of fluorometric detection was 0.0324 μg/L(S/N=3).In addition,the absorption of the g-C3N4/AgNPs at 390 nm decreased because of the aggregation of the AgNPs,but was recovered in presence of OPs because of the inhibition of enzyme activity by OPs.This method was successfully applied to the analysis of parathion-methyl in real samples.Chapter 4:A highly sensitive and selective method for double-signal(fluorescence and UV-vis spectrophotometry)analysis of OPs was developed based on graphene quantum dots(GQDs)modified AgNPs.Since the inner filtration effect(IFE),AgNPs can effectively inhibit fluorescence of GQDs as a fluorescent absorber.ATCh was catalyzed by AChE to produce thiocholine(TCh),which would induce aggregation of AgNPs,thereby recovering the fluorescence.However,the fluorescence of GQDs/AgNPs was quenched again.due to the inhibitory effect of OPs on ATCh.Furthermore,the degree of quenching was proportional to the OPs concentration with limit of detection(LOD)as low as 0.017 μg/L.On the other hand,the UV-visible absorption of GQDs/AgNPs at 390 nm decreased on account of the aggregation of AgNPs,but the absorption would recover linearly when exited OPs.The methods were successfully applied to the analysis of OPs in real samples.The innovation points of this paper mainly include:(1)abundant raw materials,low cost and low requirement for equipment,the construction of complex sensors to detect pesticide residues in water,and good sensitivity and selectivity;(2)low toxicity,good solubility and high biocompatibility of fluorescent materials.These characteristics make it have a lot of potential applications,with good development prospects and application prospects.